The present invention relates to processes for simultaneously treating and extracting groundwater, more specifically of passing gas through groundwater in multiple successive stages as it is pumped out of a well for the purpose of chemically or physically altering the groundwater to condition it for various uses upon discharge.
One such application is air stripping of contaminated groundwater to remove Volatile Organic Compounds as part of a "pump and treat" or in-situ recirculation type system for groundwater remediation. Many sites of groundwater contamination include Volatile Organic Compounds (VOCs) which are removed by "pump and treat" systems that extract contaminated groundwater with electric pumps, transport the extracted water to a central treatment facility, remove VOCs by above ground air stripping devices, and then discharge the treated effluent. These systems can be effective in providing subsurface hydraulic capture and containment of contaminant plumes and in removing VOCs from the extracted water to allow disposal by various means, however they can be expensive, incorporate specialized proprietary manufactured equipment, require professional consultants for design and/or operation, require expensive pilot testing, and in the case of "packed tower" aerators be visually imposing.
Other methods of groundwater cleanup include in-well aeration by air-lift pumping with reinjection of the water into the surrounding soils and/or recirculation of contaminated groundwater through a vadose (unsaturated) zone in which Soil Vapor Extraction can be employed to remove VOCs, but it is unclear if such an arrangement can be configured to provide hydraulic capture and containment of contaminant plumes since little or no water is removed from the affected hydraulic formation(s). Also, in such systems otherwise uncontaminated soils may be contaminated by partially treated groundwater percolation in the recirculation process. These methods may also not work in geologic settings void of a sufficiently permeable formation above the water bearing zone being treated to which the treated water can be effectively reinjected or recirculated either by gravity or mechanical means.
One object of the present invention is to provide a simple and inexpensive method for removing VOCs from groundwater. The invention uses widely available common piping and hardware components to construct an in-well device to air-strip VOCs from groundwater during the pumping process. It's claimed advantages over the current common practice of electric pumping and above ground air stripping include substantial cost savings, ease of installation and removal, greater dispersion of VOC discharges to the atmosphere, ability to tailor cleanup efforts at individual well sites, and easier maintenance with less chances of biological or chemical fouling of pumping or air stripping equipment. It's claimed advantages over previous in-well or in-situ air stripping treatment methods include a higher efficiency of VOC removal per pumping pass than systems which employ recirculation of the extracted groundwater to the surrounding geologic formation. This system also improves the feasibility of in-well air stripping at sites where the geology is not conducive to recirculation of the water through the geologic formation for additional treatment by either more passes of in-well stripping. SVE in the vadose zone, or a combination of the two.
Other objects of the invention are to inject gasses other than air into the groundwater to modify characteristics such as pH or metal concentrations, or to condition the temperature of the groundwater prior to discharge by the addition or removal of heat from the water by the injected gas.
The novel features and characteristics of the invention are set forth particularly in the claims herein. Additional objects and advantages will be set forth in the description and drawings or will be evident from them taken in conjunction or will be learned from the construction, operation, and maintenance of the invention.